Efficacy of Universal Nucleic Acid Amplification Test Admission Screening and Combined Infection Prevention Strategies for Asymptomatic Patients Against Nosocomial COVID-19 Transmission in a Longitudinal Fluctuating Epidemic Setting

Background: COVID-19 is contagious among even asymptomatic patients. Universal test-based admission screening has been tried to prevent nosocomial transmission from asymptomatic patients. We aimed to analyze the effectiveness of universal screening and a combined infection prevention strategy on admissions over a long period in a fluctuating high-prevalence setting.Methods: A retrospective cohort study at Tokyo Medical University Hospital, from 11 May 2020 to 30 September 2021, provided the data for universal nucleic acid amplification test (NAAT) admission screening and combined infection prevention strategies for all inpatient admissions. The primary outcome was COVID-19 in patients after admission. The secondary outcomes were total positive numbers, time-series analysis of monthly positive numbers, positive rates of universal admission NAATs, clinical features in positive cases of universal admission NAATs, and nosocomial transmission.Findings: The total 38,113 NAATs included 32,081 admission NAAT screenings. The total positive rate was 1.4% (557 of 38,113). The positive rate in admission screenings of the asymptomatic population was 0.11% (32 in 29,556). The positive rate for the symptomatic population was 13.2% (334 of 2,525). Five inpatients developed COVID-19. A nosocomial transmission was related to COVID-19 in 2 patients and 3 healthcare workers. Another 3 patients were sporadic cases. No additional nosocomial transmission occurred with combined infection prevention strategies.Interpretation: This study illustrated the effectiveness of universal SARS-Cov-2 NAAT admission screening during fluctuating epidemic surges. Despite incomplete test-based admission screenings, combined infection prevention strategies were effective and could improve the defects of test-based admission screening.Funding Information: No funding or sponsorship was received for this study or publication of this article. The Rapid Service Fee was funded by the authors.Declaration of Interests: The authors declare that they have no competing interests.Ethics Approval Statement: This study was approved by the Ethical Committee of Tokyo Medical University (approval number: T2020-0161). The need for consent was formally waived by the Ethical Committee of Tokyo Medical University. This study was performed in accordance with the Helsinki Declaration of 1964 and its later amendments.